Disk management method, disk management device and storage system

ABSTRACT

A disk management method for managing a disk management device for writing and reading data to and from a disk drive in which a recording medium is managed in a first control unit. The disk management method includes an error checking operation for checking an error on the recording medium in the first control unit, an error correction operation for correcting the error detected in the error, an error correcting operation for correcting the error detected in the error checking operation after converting data including the error to the second control unit, a data loss registration operation for registering a region in which data are lost due to an inconsistency between the first control unit and second control unit in a data loss region table, and a data loss recovery operation for recovering the loss of data with reference to the data loss region table.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is related to and claims priority to Japanese patentapplication no. 2007-282339 filed on Oct. 30, 2007 in the Japan PatentOffice, the entire contents of which are incorporated by referenceherein.

BACKGROUND OF THE INVENTION

1. Field

An aspect of the present invention relates to a disk management device,a storage system and a disk management method that manage data writingto and data reading from a disk drive. An aspect of the presentinvention may include a disk management device, a storage system and adisk management method in which a disk drive and a disk managementdevice manage data in different control units.

2. Description of the Related Art

Recently, the capacity of recording media has been increased by atechnique in which accesses to multiple disk drives are managedcollectively by a disk management device. Typically, the storage systemshave an error-correcting function to achieve greater levels ofreliability.

Japanese Laid-open Patent Publication 2006-268673 discloses a techniquein which all sectors subsequent to an incomplete-write sector arechecked for errors when writing a series of data onto multiple sectorshas failed and been suspended is known.

Japanese Laid-open Patent Publication 2006-31332 discloses a techniquein which disk drives have a redundant configuration is also known.Losses of data in a disk drive are checked and recovered in a checkprocess to restore the redundancy.

Conventional storage systems use a Fiber Channel (FC) disk or a SerialAttached SCSI (SAS) disk. The FC disk and the SAS disk are partitionedby 520-byte block-512 bytes for data and 8 bytes for block checkcharacter. Data stored on the disks are managed by logical blockaddresses (LBA) assigned to each block. Thus, the disk management devicecontrols accesses to the disk with LBAs assigned to each 520-byte blockas well.

There has been a demand of realizing a technique in which the diskmanagement device managing data with the 520-byte control unit managesdisks on which data are managed with LBAs assigned to 512-byte blocks,such as a SATA disk. Managing disks on which data are managed indifferent control units may reduce costs on an entire system byutilizing inexpensive disks in parallel with utilizing conventionalmanagement device configuration.

However, where data stored on the disks and in the disk managementdevice are managed in different control units, LBAs assigned to thedisks may be inconsistent with LBAs assigned to the disk managementdevice. Data are recovered based on the LBA when an error occurs.However the inconsistency may contribute to loss of data in an errorcorrection process.

SUMMARY

In accordance with an aspect of an embodiment, a disk management methodmanages a disk management device for writing and reading data to andfrom a disk drive, in which a recording medium is managed in a firstcontrol unit, the disk management method includes an error checkingoperation for checking an error on the recording medium in the firstcontrol unit, an error correction operation for correcting the errordetected in the error, an error correcting operation for correcting theerror detected in the error checking operation after converting dataincluding the error to the second control unit, a data loss registrationoperation for registering a region in which data are lost due to aninconsistency between the first control unit and second control unit ina data loss region table, and a data loss recovery operation forrecovering the loss of data with reference to the data loss regiontable.

The above-described embodiments of the present invention are intended asexamples, and all embodiments of the present invention are not limitedto including the features described above.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 illustrates a schematic view of the storage management device;

FIG. 2 illustrates a read process executed by the storage managementdevice;

FIG. 3 illustrates a write process executed by the storage managementdevice;

FIG. 4 illustrates a recovery process executed by the storage managementdevice (part 1);

FIG. 5 illustrates the recovery process executed by the storagemanagement device (part 2);

FIG. 6 illustrates a data loss recovery process executed by the storagemanagement device;

FIG. 7 is a flow chart illustrating a check process executed by thestorage management device; and

FIG. 8 illustrates a schematic view of the storage system.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

Reference may now be made in detail to embodiments of the presentinvention, examples of which are illustrated in the accompanyingdrawings, wherein like reference numerals refer to like elementsthroughout.

The disk management method, the disk management device and the storagesystem according to an embodiment of the present invention will bedisclosed.

FIG. 1 illustrates the schematic view of storage management device 10.Storage management device 10 connects to disk drives D1 and D2. Storagemanagement device 10 includes a main controller 11, a control unitconverter 12, a switch chip 13 and a data loss management table 14 asshown in FIG. 1.

Main controller 11 controls storage management device 10 completely.Main controller 11 has an access processor 11 a, a check processor 11 band an error corrector 11 c. Access processor 11 a handles accesses suchas write requests and read requests from an external terminal (not shownin FIG. 1) to the disks.

Check processor 11 b cyclically checks the disks mounted in the diskdrives connected to storage management device 10 for errors. Errorcorrector 11 c corrects errors of the disks detected in accessing orchecking the disks. Each disk mounted in disk drive D1 stores mirrorcontents of disks mounted in disk drive D2. Storing mirror contents ofdisks provides a redundant configuration. If an error occurs on eitherside of the mirror, data are reconstructed from the data stored on theother side of the mirror.

Switch chip 13 switches an access destination of storage managementdevice 10. Control unit converter 12 converts control units. Switch chip13 switches a disk to be accessed from storage management device 10.

Disk drives D1 and D2 mount SATA disks. Disc drive D1 and disk drive D2are a mirrored pair, included in the redundant array. The disk drivesmanage data writing and reading to or from the recording media mountedtherein with LBAs assigned to every 512-byte-block (hereinafter referredto as LBA512).

Storage management device 10, on the other hand, manages accesses to thedisk with LBAs assigned to every 520-byte-block (hereinafter referred toas LBA520). The difference between the control units will be solved byconverting the addresses by control unit converter 12.

Control unit converter 12 includes disk management device buffer 12 aand disk buffer 12 b. Control unit converter 12 handles accesses afterconverting the addresses using these buffers.

FIG. 2 illustrates the read process executed by storage managementdevice 10. A region of the recording medium to which LBA520 0x101 wasassigned corresponds to regions to which LBA512s 0x101 and 0x102 wereassigned as shown in FIG. 2.

The data from the regions to which LBA512s 0x101 and 0x102 were assignedare read first, in order to read data stored in the region to whichLBA520 0x101 was assigned. The data are then buffered in disk buffer 12b. Secondly, a portion matching the data stored in the region to whichLBA520 0x101 is assigned is extracted from the data buffered in diskbuffer 12 b. The extracted data are buffered in disk management devicebuffer 12 a. Thus, the read request with the LBA520 to disk drive D1 isexecuted in which data are managed with LBA512s.

FIG. 3 illustrates the write process executed by storage managementdevice 10. To write data in the region to which LBA520 0x101 wasassigned, firstly, the data are buffered in disk management devicebuffer 12 a as shown in FIG. 3. At the same time, the data stored in theregions to which LBA512s 0x101 and 0x102 were assigned, and in whichdata stored in the region to which LBA520 0x101 was assigned areincluded, are read out and then buffered in disk buffer 12 b.

Secondly, the data buffered in disk management device buffer 12 a aremerged into the corresponding portion of the data buffered in diskbuffer 12 b. Thereafter, the data are written back to disk drive D1.Thus, the write request with LBA520 to disk drive D1 is executed inwhich data are managed with LBA512s.

The recovery process to recover data stored in disk drive D1 from errorswill be discussed with reference to FIGS. 4 and 5. Consider an erroroccurring in the region of the recording medium mounted in disk drive D1to which LBA512 0x102 was assigned. The region to which LBA512 0x102 wasassigned corresponds to the regions to which LBA520s 0x101 and 0x102were assigned. Error corrector 11 c recognizes that the error occurs inthe region to which the lower number was assigned, in this case, LBA5200x101.

Error corrector 11 c recovers the data stored in the region of therecording medium mounted in disk drive D1 to which LBA520 0x101 wasassigned by using corresponding data stored in disk drive D2. Firstly,error corrector 11 c reads out the data stored in the region of therecording medium mounted in disk drive D1 to which LBA520 0x101 wasassigned as shown in FIG. 4. Since the region to which LBA520 0x101 wasassigned corresponds to the regions to which LBA512s 0x101 and 0x102were assigned, the data stored in the regions to which LBA512s 0x101 and0x102 were assigned are read out from the disk buffer. If the errorcorrector 11 c fails to read the data stored in the region assignedaddress 0x102 because of the error, the damaged data are replaced withdummy data consisting of 0s.

Secondly, data stored in the corresponding region of the recordingmedium mounted in disk drive D2 are read out as shown in FIG. 5. Thesame data of the data stored in the region of the recording mediummounted in disk drive D1 to which LBA520 0x101 was assigned are storedin the region of the recording medium mounted in disk drive D2 to whichLBA520 0x101 was assigned as shown in FIG. 5. Likewise, in the readprocess, the data stored in the region of the recording medium mountedin disk drive D2 to which LBA520 0x101 was assigned are read out. Sincethe data read out from disk drive D2 are duplicated from the data storedin the region of the recording medium mounted in disk drive D1 to whichLBA520 0x101 was assigned, the data are identical to the intactoriginal.

Thirdly, the data read out from the region of the recording mediummounted in disk drive D2 to which LBA520 0x101 was assigned are mergedinto the data stored in the disk buffer in a manner similar to that ofthe write process described above. The data are then written back todisk drive D1.

Thus, the data stored in the region of the recording medium mounted indisk drive D1 to which LBA520 0x101 was assigned are restored to theoriginal state. Although a part of the data stored in the region towhich LBA512 0x102 was assigned are restored, that which corresponds tothe data stored in the region to which LBA520 0x101 was assigned are notrestored. The data which is not restored corresponds to the data storedin the region to which LBA520 0x102 was assigned, which was replacedwith the dummy data. In short, a part of data stored in the regionassigned LBA512 0x102 of the recording medium mounted in disk drive D1is lost.

Error corrector 11 c registers the region in which the data were lost inthe recovery process in the data loss management table 14 shown inFIG. 1. In this case, the data in the region assigned address 0x102 werelost. The data loss region registered in data loss management table 14is recovered when the disk is accessed with the address of the region orchecked by check processor 11 b by simulating a psuedo error occurrenceto execute the recovery process.

Recovering lost data will be disclosed with reference to FIG. 6.Firstly, when an error is detected in the region of the recording mediummounted in disk drive D1 to which LBA512 0x102 was assigned, the dataincluding the error are recovered in the recovery process describedabove. During the process, an address of the region in which the dataare lost due to the difference between the first control unit and thesecond control unit is registered in data loss management table 14.

Secondly, the data loss management table 14 is referenced the next timedisk drive D1 is checked or accessed, and the error occurring in theregion registered in the data loss management table is reported. Errorcorrector 11 c executes the recovery process described above to recoverthe data in response to the pseudo error by compensating for the lossfrom duplicated data stored in disk drive D2.

The recovery process in response to the pseudo error is similar to theprocess in the event of an actual error. However, the error is pseudo,so the data are read out from disk drive D1 successfully. Thus, the datais not substituted with dummy data, preventing another loss of data.

The check process executed by storage management device 10 will bedisclosed with reference to FIG. 7. Firstly, check processor 11 bselects a disk to be checked for errors (operation S101). Secondly, dataloss management table 14 is referenced (operation S102). Thirdly, errorcorrector 11 c recovers the error included in the region at the addressregistered in data loss management table (operation S104) when theselected disk includes the region registered in the table (operationS103, Yes). Thereafter, the registration of the address is deleted fromdata loss management table 14 (operation S105).

Where no data losses of the selected disk are registered (operationS103, No), or after recovering the data loss, then check processor 11 bchecks the selected disk for errors (operation S106).

Where an error is detected (operation S107, Yes), error corrector 11 crecovers a region in which the error is detected (operation S108). Thenan address of the region in which the data are lost during the recoveryis registered in data loss management table 14 (operation S109). Thenthe process is completed.

As described above, the address of the region in which a part of thedata is lost due to the inconsistency between the control units isregistered in data loss management table 14. The loss is recovered inthe next checking by simulating the pseudo error occurrence in theregion at the address registered. Accordingly, the conventional storagedevice 10 may be used without any changes.

Data loss management table 14 may be referenced before anything else notonly in checking but also in issuing a read request to a disk. It isdesirable to report a pseudo error to recover the loss when an addressof a data loss region that corresponds to the read request isregistered.

Where a write request is issued to a disk and an address corresponds tothe write request is registered in data loss management table 14, theloss is compensated for by the writing. Therefore, the registration willbe deleted from data loss management table 14.

FIG. 8 illustrates a schematic view of an example of the storage systemaccording to the present invention. The storage system in FIG. 8includes main storage device 1 and expansion storage device 2 connectedto main storage device 1.

Main storage device 1 has storage management device 20 having the samestructure of storage management device 10 previously described and diskdrives D1 through Dn. Expansion storage device 2 expands disk drivesmanaged by main storage device 1. Expansion storage device 2 has switchchips 13 a and 23 a, and disk drives D1 a through Dna. Additionally,expansion storage device 2 may further connect to an expansion storagedevice not shown in FIG. 8.

The storage system has the storage management devices having redundantconfigurations and the expanded disk drives. Accordingly, higherreliability and a larger capacity are achieved.

According to the aspect of the present invention, data losses arerecovered by registering the addresses of regions in which data are lostin error correction and simulating pseudo errors in the regions at theaddresses registered where the disk management device manages disks inwhich data are managed in the different control unit.

Accordingly, the data losses are recovered by simulating the pseudoerror occurrence in checking the disk drive or in accessing to the diskdrive as well as in the event of actual errors. Therefore, aconventional device may be used effectively.

It is not desired to limit the inventive embodiments to the exactconfigurations and operations illustrated and described. In thisembodiment, disk drive D1 is mirrored by disk drive D2. However, thepresent invention may be applicable to a disk configuration in RAID5 orRAID6.

Although a few preferred embodiments of the present invention have beenshown and described, it would be appreciated by those skilled in the artthat changes may be made in these embodiments without departing from theprinciples and spirit of the invention, the scope of which is defined inthe claims and their equivalents.

1. A disk management method for managing a disk management device forwriting and reading data to and from a disk drive, in which a recordingmedium is managed in a first control unit, the disk management methodcomprising: checking an error on said recording medium in said firstcontrol unit; correcting the error detected in said error checkingoperation after converting data including the error to a second controlunit; registering a region in which data are lost due to aninconsistency between said first control unit and second control unit ina data loss region table; and recovering the loss of data with referenceto the data loss region table.
 2. The disk management method accordingto claim 1, further comprising: referring to said data loss region tablein checking said recording medium cyclically for an error; andrecovering the region when the data loss region of said recording mediumis registered in the data loss region table.
 3. The disk managementmethod according to claim 1, further comprising: referring to said dataloss region table when a read request to a specific disk is issued; andrecovering the region when the data loss region of the disk isregistered in said data loss region table.
 4. The disk management methodaccording to claim 1, wherein said disk drive has a redundantconfiguration, and a region in which an error occurs or data are lost isrecovered using said redundant configuration during said errorcorrecting or the lost data recovering.
 5. The disk management methodaccording to claim 1, wherein said data is block data.
 6. A diskmanagement method for managing a disk management device for writing andreading data to and from a disk drive, in which a recording medium ismanaged in a first control unit, the disk management method comprising:checking an error on said recording medium in said first control unit;correcting the error detected in said error checking operation afterconverting data including the error to a second control unit;registering a region in which data are lost due to an inconsistencybetween said first control unit and second control unit in a data lossregion table; recovering the loss of data with reference to the dataloss region table; and recovering the data loss region registered insaid data loss region table by simulating an error occurrence in theregion and deleting a registration of the region from said data lossregion table.
 7. The disk management method according to claim 6,further comprising: deleting the registration of the data loss region insaid data loss region table when a write request to a specific disk isissued and the region corresponds to the write request.
 8. The diskmanagement method according to claim 6, wherein said recording medium ispartitioned by said first control unit by 512 bytes as a block and saidsecond control unit partitions said recording medium by 520 bytes as ablock.
 9. A disk management device for managing writing and reading datato and from a disk drive in a second control unit, in which a recordingmedium is managed in a first control unit, the disk management devicecomprising: an error checker for checking an error on said recordingmedium in said first control unit; an error corrector for correcting theerror detected by said error checker after converting data including theerror into said second control unit; a data loss region table forstoring a region in which data are lost due to an inconsistency betweenthe first control unit and the second control unit; and a data lossrecovery unit for recovering a data loss with reference to said dataloss region table.
 10. A disk management device for managing writing andreading data to and from a disk drive in a second control unit, in whicha recording medium is managed in a first control unit, the diskmanagement device comprising: an error checker for checking an error onsaid recording medium in said first control unit; an error corrector forcorrecting the error detected by said error checker after convertingdata including the error into said second control unit; a data lossregion table for storing a region in which data are lost due to aninconsistency between the first control unit and the second controlunit; and a data loss recovery unit for recovering a data loss withreference to said data loss region table: wherein said data lossrecovery unit reports that an error occurs in the region registered insaid data loss region table to said error corrector to correct the errorand then deletes a registration of the data loss region from said dataloss region table.
 11. The disk management device according to claim 9,wherein said data loss recovery unit refers to said data loss regiontable where a read request to a specific disk is issued.
 12. The diskmanagement device according to claim 9, wherein said disk drive has aredundant configuration and said error corrector or data loss recoveryunit recover a region in which an error occurs or data are lost by usingsaid redundant configuration.
 13. The disk management device accordingto claim 9, wherein said data loss recovery unit refers to said dataloss region table in checking said recording medium cyclically for anerror.
 14. The disk management device according to claim 10, wherein aregistration of a data loss region registered in the data loss regiontable is deleted when a write request to a specific disk is issued andthe region corresponds to the write request.
 15. A storage systemcomprising a disk drive for managing a recording medium in a firstcontrol unit and a disk management device for managing writing andreading data to and from said disk drive in a second control unit, inwhich a recording medium is managed in a first control unit, the storagesystem comprising: an error checker for checking said recording mediumfor an error in said first control unit; an error corrector forcorrecting the error detected by said error checker after convertingdata including the error into said second control unit; a data lossregion table for storing a region in which data are lost due to theinconsistency between said first control unit and the second controlunit; and a data loss recovery unit for recovering a data loss withreference to said data loss region table.
 16. The storage systemaccording to claim 15, wherein said data loss recovery unit refers tosaid data loss region table in checking said recording medium cyclicallyfor an error.
 17. The storage system according to claim 15, wherein saiddata loss recovery unit refers to said data loss region table when aread request to a specific disk is issued.
 18. The storage systemaccording to claim 15, wherein said disk drive has a redundantconfiguration and said error corrector or data loss recovery unitrecover a region in which an error occurs or data are lost by using saidredundant configuration.
 19. A storage system comprising a disk drivefor managing a recording medium in a first control unit and a diskmanagement device for managing writing and reading data to and from saiddisk drive in a second control unit, in which a recording medium ismanaged in a first control unit, the storage system comprising: an errorchecker for checking said recording medium for an error in said firstcontrol unit; an error corrector for correcting the error detected bysaid error checker after converting data including the error into saidsecond control unit; a data loss region table for storing a region inwhich data are lost due to the inconsistency between said first controlunit and the second control unit; and a data loss recovery unit forrecovering a data loss with reference to said data loss region table;wherein said data loss recovery unit reports that an error occurs in aregion registered in said data loss region table to said error correctorto recover the error and then deletes a registration of the data lossregion from said data loss region table.
 20. The storage systemaccording to claim 19, wherein a registration of a region registered insaid data loss region table is deleted when a write request to aspecific disk is issued and the region corresponds to the write request.